The proposed research intends to evaluate the functional significance of surface glycoproteins of hemopoietic stem cells (CFU) which produce macroscopically visible spleen colonies in transplanted, irradiated hosts and which provide survival value to these animals. Glycoprotein terminal sugars will be removed with a variety of glycosidases and the proteins themselves with proteolytic enzymes. The effects of these perturbations will be studied in terms of (1) the cell's ability to bind into the host spleen and (2) the cell's ability to respond to erythropoitin the specific inducer of erythropoiesis leading to the synthesis of hemoglobin. The repair of the enzyme sheared surfaces will be investigated both in vivo and in vitro. The information gained from the above studies on cell surfaces will be exploited in an attempt to provide a more adequate substrate for cultivation of the stem cell based on the notion that media is not the only prerequisite for successful in vitro cultures but that surface is at least as important. In addition the characterization of cell surfaces can provide useful information concerning the potential separation of various cell types from the parent tissues. In these studies affinity type supports derivitized with antibodies and lectins which bind specifically to the cell's surface will be used. This successful development for separation and in vitro culture will provide cells for the health sciences for future studies of therapeutic control of neoplastic growth.